Vehicle driveshaft

ABSTRACT

A vehicle driveshaft  10  having first and second splined members  12, 16  which are manufactured of aluminum, which are anodized, and which respectively include relatively long and wide respective spline portions  14, 18 , thereby cooperatively forming a relatively stiff driveshaft  10.

FIELD OF THE INVENTION

[0001] This invention relates to a vehicle driveshaft and moreparticularly, to a relatively stiff vehicle driveshaft which isrelatively light in weight and which includes relatively long splinedportions having relatively large and/or wide spline pitch diameters andworking areas.

BACKGROUND OF THE INVENTION

[0002] A vehicle driveshaft is typically and operatively mounted to atransmission assembly and to a differential assembly and, moreparticularly, transfers the transmission produced torque to thedifferential, thereby causing the vehicle wheels to be desirably andselectively turned. The driveshaft also dynamically compensates for thechange or modification in the distance between the transmission and thedifferential which occurs as the vehicle is driven. Hence, thedriveshaft includes a portion or a member which typically andtelescopingly moves along the longitudinal axis of the driveshaft inresponse to relative movement between the differential and thetransmission (e.g., the driveshaft is capable of dynamically modifyingits length in response to the movement of the vehicle).

[0003] This dynamic length modification is typically achieved by the useof a pair of splined members which are normally manufactured of arelatively heavy material, such as conventional and commerciallyavailable iron, and which are respectively and commonly referred to asthe “slip yoke” and the “yoke shaft”. Particularly, the yoke shaftmember is selectively inserted into the slip yoke and is movably coupledto the transmission. The slip yoke is typically coupled to thedifferential and the respective splines of these members (which aretypically broached or “machined” onto the yoke members) intermeshinglycooperate to allow and/or to cause the yoke shaft to rotate the slipyoke in response to the rotation of the transmission, thereby allowingthe transmission produced torque to be selectively coupled to thedifferential by the rotation of the slip yoke. The intermeshed splinesalso allow the yoke shaft to be movable along the longitudinal axis ofthe driveshaft, thereby allowing the driveshaft to dynamicallycompensate for changes in the distance between the transmission and thedifferential and allowing the driveshaft to desirably operate as thevehicle is driven. While these driveshafts allow for the desiredcommunication of the transmission-produced torque to the differential,they suffer from some drawbacks.

[0004] First, the yoke members of these prior driveshafts are normallyand rather loosely connected because the respective splines aretypically formed on only relatively small or relatively short portionsof the respective and relatively heavy yoke members. These relativelyshort intermeshing splined portions allow the engaged members toundesirably “wobble” as the vehicle is driven and produce undesirablenoise and vibrations which are undesirably communicated into thepassenger compartment. These relatively short “yoke engagement” portionsalso cause undesirable “backlash” to occur as the transmission generatedtorque is transferred to the slip yoke member. Secondly, the relativelyheavy yoke members require relatively narrowly formed and narrowlyspaced splines which cause the engaged members to experience relativelyhigh stress and loads and which further cause undesirable fatigue and/orfailure of the splines and/or of the engaged yoke members. Additionally,the relatively heavy material used to form the yoke members requires theyoke members to have a relatively small diameter to avoid theundesirable addition of weight to the vehicle. These relatively smalldiameter members further cooperatively provided only a relativelylimited or small amount of “engaging” surface or “working” area betweenthe intermeshing yoke members, thereby further causing relatively highstress and loads to be applied and/or transferred among and between theengaged members. Finally, the engaged yoke members are prone toundesirably “buckle” during and/or as a result of a vehicle accident,thereby undesirably damaging many of the vehicle underbody components,including but not limited to, the vehicle fuel tank.

[0005] There is therefore a need for a new and improved vehicledriveshaft which overcomes many, if not all, of the previouslydelineated drawbacks of such prior vehicle driveshafts.

SUMMARY OF THE INVENTION

[0006] It is a first object of the invention to provide a vehicledriveshaft which overcomes at least some of the previously delineateddrawbacks of prior vehicle driveshafts.

[0007] It is a second object of the invention to provide a relativelylightweight vehicle driveshaft having a pair of selectively hardened,engaging, and intermeshing splined members which cooperatively allow forthe formation of a relatively stiff vehicle driveshaft.

[0008] It is a third object of the invention to provide a vehicledriveshaft having a pair of selectively engaging and intermeshingsplined members, each of the splined members respectively containingrelatively long and relatively widely spaced splines which form and/orwhich contain relatively wide or large “pitch diameters” and/or “workingareas”.

[0009] It is a fourth object of the invention to provide a vehicledriveshaft having a pair of selectively engaging and intermeshingsplined members which are respectively engaged and/or are operativelycoupled along a relatively long engagement and/or coupling distance.

[0010] It is a fifth object of the invention to provide a vehicledriveshaft having a pair of intermeshing splined members having arespective and a relatively large diameter.

[0011] According to a first aspect of the present invention, a vehicledriveshaft is provided and includes a pair of aluminum members, each ofthe aluminum members being of a certain respective length and having acertain respective diameter of a certain respective value. Each of thepair of aluminum members has a respective splined portion which has arespective length equal to about three times the value of one of therespective diameters and the respective splined portions intermeshinglycooperate to form a relatively stiff vehicle driveshaft.

[0012] According to a second aspect of the present invention, a methodis provided to increase the stiffness of a driveshaft of the type havinga first member, and a second member which movably extends a certainlength within the first member. The method includes the steps ofincreasing the certain length.

[0013] According to a third aspect of the present invention, a vehicledriveshaft is provided and is formed by the process of providing a firstand a second aluminum member; forming splines within the first and thesecond aluminum members; coating the formed splines with a hard anodizedcoating; and placing the first member into the second member, therebycooperatively forming a driveshaft by the use of the first and thesecond members.

[0014] These and other features, aspects, and advantages of theinvention will become apparent by reading the following specificationand by reference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is an unassembled perspective view of a vehicle driveshaftwhich is made in accordance with the teachings of the preferredembodiment of the invention;

[0016]FIG. 2 is assembled side view of the driveshaft which is shown inFIG. 1; and

[0017]FIG. 3 is a side view of the driveshaft taken along view line 3-3;

[0018]FIG. 4 is a fragmented perspective view of the portion of thedriveshaft which is shown in FIG. 3 and which illustrates portions ofthe splines which are used and/or selectively formed upon the vehicledriveshaft of the preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

[0019] Referring now to FIGS. 1 through 4, there is shown a driveshaft10 which is made in accordance with the teachings of the preferredembodiment of the invention. As shown, driveshaft 10 includes agenerally round and/or tubular and generally hollow member 12 having asplined portion 14 which is circumferentially formed upon the exteriorsurface 15 of member 12. Driveshaft 10 further includes a secondgenerally round and/or tubular and generally hollow member 16 having asplined portion 18 which is circumferentially formed upon the innersurface 19 of member 16 and which is adapted to selectively andcooperatively intermesh with a splined portion 14. Members 12, 16 haverelatively large respective diameters 50, 52 which in one non-limitingembodiment are respectively equal to about approximately four (4.0)inches to about four and one-half (4.5) inches. Other larger diametervalues may be utilized according to the teachings of this invention.

[0020] Member 12 is adapted to selectively, movably, and telescopinglypenetrate member 16 and to allow splined portions 14, 18 tocooperatively intermesh in the usual and known manner. Particularly, asshown, member 16 is movably coupled, by the use of a conventional flange20, to a conventional transmission 21, while member 12 is movablycoupled, by the use of a conventional flange 22, to a conventionaldifferential 23. The torque, supplied by the transmission 21 iscommunicated to member 16 and then, by use of the intermeshed splineportions 14, 18, to member 14 and to the differential 23.

[0021] As further shown, driveshaft 10 includes a substantially roundand generally tubular shaped vibration dampening member 24, which isadapted to conform to the shape of the selectively and movably engagedmembers 12, 16 and which is removably and selectively placed within theassembled members 12, 16. Particularly, member 24 absorbs at least someof the vibrational energy which is generated by the operativelyassembled members 12, 16. Member 24 may be formed from conventional andcommercially available cardboard and/or from a variety of othervibration dampening materials.

[0022] In one non-limiting embodiment of the invention, a rubber bootmember 26 having several integrally formed and selectively expandablepleats 27 substantially covers the intermeshed portions 14 and 18 and isclamped onto the driveshaft 10 by the use of a pair of substantiallyidentical and commercially available generally circular clamps 28, 30.In one embodiment, the boot member 26 selectively “slips” or “slides”over the splined portions 14, 18 in the manner shown. The cooperatingspline portions 14, 18 also allow member 12 to dynamically move alongthe longitudinal axis of symmetry 32 of the driveshaft 10 in response tochanges in the distance between the transmission 21 and the differential23, in a known manner.

[0023] In the preferred embodiment of the invention, the members 12 and16 are manufactured from conventional and commercially availablelightweight aluminum material which may comprise a commerciallyavailable “6061-T4” type of aluminum or aluminum alloy material. Thesplines are “cold formed” upon the portions 16, 18 by the use of theconventional “Grob” process which is provided by the Grob corporation ofMannedorf, Switzerland. Moreover, splined portions 14, 18 areselectively hardened or “anodized” in accordance with the commerciallyavailable Metalast anodizing process which is provided by the Metalastcorporation of Minden, Nev. More particularly, the splined portions 14,18, in one non-limiting embodiment, are anodized with a layer of“Metalast hardcoat” material having a thickness of about 0.002″.

[0024] Importantly, the use of such anodized aluminum and cold-formedspline portions 14, 18 allows for a relatively light-weight driveshaft10 which substantially reduces the amount of vibration and noise whichemanates from the operatively formed driveshaft 10. The relativelylightweight aluminum construction allows members 12, 16 to haverelatively large diameters 50, 52, while providing a significantdecrease in the overall weight relative to prior driveshafts. Theserelatively large diameter members 50, 52 efficiently distribute theapplied axial loads over a larger surface area, thereby allowingdriveshaft 10 to support relatively larger torques at relatively higherspeeds than prior driveshaft assemblies. Further, this relativelylight-weight design allows for relatively long spline portions 14, 18which, in the preferred embodiment, each have a substantially identicallength 56 equal to at least and approximately three times the diameter52 of member 16 (e.g., approximately 13.5 inches). In other alternatenon-limiting embodiments, splines 14, 16 have lengths which respectivelyextends approximately half way along members 12, 16 or have respectivelengths equal to approximately three times their respective diameter.The anodized aluminum splines also, as is best shown in FIGS. 3 and 4,allow for a relatively large and/or wide splined mating surfaces and/or“working areas” (e.g., which in one non-limiting embodiment have a“pitch diameter” 42 equal to about ten to about twenty millimeters).These wide splines allow for better distribution of the axial loadsimparted upon portions 14, 18 effective to reduce the overall wear ofthe splines and the assembly 10, thereby substantially increasing the“working” or “operating” life of the driveshaft 10.

[0025] In one non-limiting, embodiment, each end wall 44, 46 of eachspline cooperatively forms an angle 48 of about sixty degrees (60°),although other angular configurations may be utilized. Further, while aportion of the splined portion 18 is shown in FIG. 3, it should berealized that splined portion 14 is substantially similar to that whichis shown in FIG. 3. Further, it should be appreciated that theserelatively long intermeshing portions 14, 18 reduce the amount of noiseand/or vibrations which are generated from the driveshaft 10, and theserelatively long splined portions 14, 18 reduce the probability that thedriveshaft 10 will undesirably buckle in a collision, thereby increasingthe overall safety of the vehicle. Further, these relatively lightweightmembers 12, 16 having relatively long respective splined portions 14, 18allow for the creation of a relative stiff and lightweight driveshaftwhich, in one embodiment, may replace and/or substantially shorten theelongated transmission extension member 21.

[0026] It is to be understood that the invention is not to be limited tothe exact construction and/or method which has been illustrated anddiscussed above, but that various changes and/or modifications may bemade without departing from the spirit and the scope of the invention.

What is claimed is:
 1. A driveshaft comprising first and second membershaving a respective diameter of a certain respective value, each of saidfirst and said second members having a respective splined portion havinga respective length of about three times said value of said respectivediameter of said first member, said second member being telescopinglyresident within said first member and said splined portion of said firstmember cooperating with said splined portion of said second member,thereby allowing said first and said second members to cooperativelyform a driveshaft.
 2. The driveshaft of claim 1 wherein said first andsaid second members are formed from aluminum.
 3. The driveshaft of claim2 wherein said splined portions are coated with an anodized hardeningsubstance.
 4. The driveshaft of claim 1 wherein said driveshaft furtherincludes a rubber boot member which overlays said splined portions ofsaid first and said second members and which is coupled to said firstand said second members.
 5. The driveshaft of claim 4 further comprisinga pair of clamps which cooperatively couple said rubber boot member tosaid first and to said second members.
 6. The driveshaft of claim 1wherein said diameter of said first member is about four and one-halfinches.
 7. A driveshaft made by the process of providing a first and asecond aluminum member; forming splines within said first and saidsecond aluminum members; hardening said formed splines by the use of ananodizing substance; and placing said first member into said secondmember, thereby cooperatively forming a driveshaft by the use of saidfirst and said second member.
 8. The driveshaft of claim 7 furthercomprising providing a rubber boot member; and placing said rubber bootmember over said splines of said first and said second member.
 9. Thedriveshaft of claim 8 further comprising providing a dampening member;and placing said dampening member into said first and said secondmember.
 10. The driveshaft of claim 7 wherein said formed splines arecold formed within said first and second members.
 11. The driveshaft ofclaim 9 wherein said dampening member comprises a cardboard member. 12.A method to increase the stiffness of a driveshaft of the type having afirst splined member and a second splined member which movably extends acertain length within the first member, said method comprising the stepsof increasing said certain length.
 13. The method of claim 12 furthercomprising the step of increasing the width of the splines on said firstand said second members.
 14. The method of claim 12 further comprisingthe step of increasing the diameter of said first and said second splinemembers.
 15. The method of claim 14 further comprising the steps ofproviding a rubber boot member; and placing said rubber boot member oversaid first and said second splined members.
 16. The method of claim 15further comprising the steps of providing a dampening member; andplacing said dampening member into said first and said second splinedmember.
 17. The method of claim 16 wherein said dampening membercomprises cardboard.